The present invention refers to a temperature control system and method for integrated circuits, particularly for those having a plurality of channels or power devices.
Most of the integrated circuits have inside a circuit (commonly referred to as Thermal Warning) that senses the silicon temperature, and when it senses a prefixed value, the circuit generates an alarm signal. This signal is usually used to turn off the devices or circuit blocks that are responsible for the excessive heat dissipation.
When such an emergency occurs all the circuits that could have generated the temperature increase are usually deactivated. However, there are applications in which totally interrupting the device functions could jeopardize the personal safety of the users or create problems to other parts of the apparatus. Therefore it has been attempted to interrupt only the channels or the devices that at that time are dissipating the most heat.
The most immediate way to realize a temperature sensor is that of using the base-emitter junction of a bipolar transistor. The voltage at the junction terminals varies with a constant gradient as the temperature varies (around xe2x88x922 mV/xc2x0 C.). Knowing the base-emitter voltage at a prefixed temperature it is possible to effect a fairly accurate measurement of this parameter.
At environment temperature the bipolar transistor, used like a temperature sensor, is off, and therefore the collector voltage is at a high level, as the temperature increases, the threshold voltage of the base-emitter junction decreases. At the prefixed temperature as activation value of the circuit, the transistor switches on and its collector signal goes to low level, signaling an anomaly.
In a multi-channel device, a method used to establish when a device anomaly occurs, in order to switch off only such a device, is that of increasing the number of temperature sensors, one for each device, and putting them near the critical points. The bias circuit of the various transistors used as temperature sensors, can be, for instance, only one, and in proximity of the critical points only the sensor used for the measurement could be placed.
With this solution a further sensor is usually combined that senses the silicon temperature in the part of the device where there is never a high power dissipation. This sensor has a more elevated temperature activation threshold than the previous sensor and has the purpose to switch off the device totally in case it reaches such a threshold.
An intrinsic problem for this type of solution is related to the temperature profiles that occur during brief transients (in the order of milliseconds) in which an elevated power is dissipated. The elevated power dissipation of a channel during a transient, seen in the proximity between the various channels placed in an integrated circuit, could make the temperature rise also in the area near the channel. In such a case, the turning off of a channel could also occur even if there is not a real malfunctioning.
Such a danger increases when the devices must work in boundary conditions, near to the thermal protection intervention temperature, such as happens for instance in automotive circuits placed in proximity to the car elements that carry the environmental temperature above 100 degrees centigrade.
In view of the described state of the art, the disclosed embodiment of the present invention provides a temperature control system for an integrated circuit that is able to identify correctly the device that is making the temperature of the integrated circuit rise.
According to one embodiment of the present invention, a temperature control system for an integrated circuit is provided, including:
at least one device that generates heat because of elevated dissipated power values;
a sensor element providing a signal correlated to the working conditions of the at least one heat generating device;
an elaboration circuit for said signal correlated to the working conditions of said at least a heat generating device;
a turning off circuit of said at least one heat generating device responsive to a signal of said elaboration circuit;
wherein said sensor element provides a signal proportional to the dissipated power of the at least one heat generating device.
A temperature control method for an integrated circuit is provided that has at least a heat generating device, and includes the following phases:
sensing the working conditions of the at least one heat generating device;
elaborating the information relative to the working conditions of the at least one heat generating device;
generating a turning off signal of the at least one heat generating device responsively to the elaborated information;
wherein the sensed working conditions are relative to the dissipated power of the at least one heat generating device.
With the device and method of the present invention, it is possible to realize a temperature control system for integrated circuits that correctly identifies the device that is overcoming the dissipation limits by obtaining the information relative to the dissipated power and not relative to the device temperature that could be altered by the nearby circuits.
Furthermore, the use of only a sensor, placed at a certain distance from the power transistors or channels, enables filtering of temperature transients that could distort the measurement and cause the turning off of a channel as well when this works correctly.